China is the largest producer of oilseed rape - one of the world's major oilseed crops. Production averages about 6 million tonnes annually (accounting for 27% of world production in 1990) from an area of 5 million hectares. Around 60% is produced as a winter crop in the central and lower Yangtse River valley. However, widespread boron (B) deficiency in the area presents a serious constraint to production.

While Chinese scientists treat crops showing acute signs of deficiency, such as floral abortion, with a B foliar-spray fertiliser, many crops with depressed yield due to B deficiency look normal, and miss being treated.

Plant and soil analysis offer prospects of much more sensitive and reliable diagnosis and prognosis of B deficiency. Likewise, critical evaluation of types of B fertiliser and rates of application should help lift production. Such investigations require special care, however - there is only a narrow margin between B deficiency and B toxicity. A further complication for the management of B nutrition of oilseed rape in China was demonstrated by recent trials at Zhejiang Agricultural University (ZAU), where high-quality cultivars were found to be more sensitive to B deficiency than traditional cultivars.

This project builds on two previous ACIAR projects, one that improved understanding of the management of B fertiliser use and another that bred high- quality oilseed rape germplasm for China. Australian scientists at Murdoch University (MU) and the Waite Institute are expert in micronutrient research, and the project leader has already studied micronutrient requirements for food legume crops in Thailand in earlier ACIAR projects. The Chinese collaborators also have a long record of micronutrient research, as well as close working links with provincial agricultural extension services. A number of exchange visits of scientists will be made between the two countries.

In China, the following four subprojects aim to increase the reliability of prediction of B deficiency in oilseed rape crops and the efficiency of the use of B fertiliser:

. Development of plant analysis standards for the diagnosis and prediction of B deficiency and toxicity in oilseed rape;
. Use of genotypic variation in the response of oilseed rape to B to manage B requirements of crops;
. Determination of the environmental factors affecting the response of oilseed rape to B; and
. Determination of the incidence and severity of B deficiency in farmers' oilseed crops by surveys of plant and soil B levels.

Field experiments and surveys in China will be supported by research in Australia. At MU, scientists will undertake glasshouse studies to develop plant analysis standards for field use to diagnose B deficiency and toxicity; and at the Waite Institute, scientists will study oilseed rape cultivar variation in response to B to determine plant traits that can be used for selection of B-efficient cultivars for screening trials in China.

In Australia areas planted to oilseed rape (canola) are increasing rapidly. Although little is known of micronutrient requirements of the crop in Australian soils, nutrient deficiencies, particularly in zinc (Zn), are highly probable. Since Zn deficiency is also common in the calcareous alluvial soils of the middle and lower Yangtse River valley, it is appropriate that the project includes complementary studies on this element. Investigations similar to those for B will be carried out for Zn in both Australia and China, and a survey in southern Australian farmers' fields will determine the incidence and severity of Zn deficiency in soil and in oilseed rape plants.

Rapeseed oil is the main cooking oil in China and nearly all the country's oilseed rape production is used domestically. In addition, rapeseed meal is a valuable component of animal feeds. Production will be increased as a result of this project: plant analysis will be used to improve the efficiency of use of B fertilisers in oilseed crops, improved guidelines will be developed for the treatment of B deficiency, and B-efficient cultivars will be identified and used to decrease B fertiliser requirements.

Australia will also benefit from development of expertise in oilseed rape nutrition, and B-efficient genotypes identified in the China program will assist in the development of B-efficient cultivars in Australia. Both countries will benefit from the complementary studies on Zn deficiency in oilseed rape.